KURT JOSTEN's great achievement as a scholar was his discovery, whilst working in the Bodleian Library in 1949, of the code in which the 17th-century antiquary Elias Ashmole had enciphered his diary.

While it is true that Ashmole's diaries and papers do not compare with those of Evelyn or Pepys, Josten's magisterial five volumes on the founder of the Ashmolean Museum, and those other institutions which have grown in Oxford from that root, were immensely detailed and scholarly. Had he not left Oxford in 1964, when his wife became ill, there can be little doubt that his achievement would have had wider recognition.

Josten was a German by birth, an Englishman by adoption, choice and taste, as well as by naturalisation in 1954. He was a native of Neuss, across the Rhine from Dusseldorf, where his family had lived since the 17th century, and a member of that unusual clan of bankers and businessmen, the Verhahns. On his first visit to England, in 1935, he felt immediately at home, and also in instant love with Oxford.

His scholarship was meticulous as was to be expected from one who was fluent in five languages, educatad by the Jesuits at Bad Godesberg from 1921 to 1929. Following a year at the Staatliches Gymnasium in Neuss, he went on to study at the universities of Geneva, Freiburg and Bonn, becoming a DCL at the University of Erlangen in 1935. By then he had abandoned his career in the law, 'as it no longer existed' in Germany, and went instead into business, banking and export. Although he denied that he had been strictly a banker, his training was beyond reproach, as he was as competent and careful in all matters relating to his personal and financial affairs as he was as a scholar.

In order to avoid conscription, having also been a passionate opponent of Nazism since 1934, he had to go into hiding in 1943, first in Paris, and then in Bavaria, where he was able to repay the shelter which the Schonborn family had given him by the protection which the American forces gave to Schloss Pommersfelden. After the war he was faced with the unenviable job of becoming the chairman of the denazification tribunal in his home-town, and, in May 1948, of going as a resettlement adviser through German prisoner-of-war camps in England and Wales, a task which he found distasteful. However, his reward was being allowed to stay in England and, in June 1948, to start working in Duke Humfrey's library in the Bodleian.

It was the existence of Ashmole's cipher transcript of the trial of Charles I with a later longhand copy which provided the essential clue for Josten's detective work on the diaries. Based on John Willis's The Art of Stenographie (1617), Ashmole's cipher is mainly phonetic, with some 200 ideographic characters of his own invention. Among his papers were the accounts of his dreams in the late 1640s which Josten had analysed retrospectively by CG Jung. They revealed 'a markedly egocentric and assertive personality', as the historian Michael Hunter wrote in 1983.

Apart from decoding Ashmole's diaries, Josten was adept at astronomy, in the history of early chemistry (alchemy), and, pre-eminently, in early astronomical instruments. Thanks to these abilities, he was appointed Curator of the Museum of the History of Science in the old Ashmolean building in Broad Street, Oxford, in 1950. He became a member of Ashmole's old college, Brasenose, in 1951, and 10 years later a Fellow of the Society of Antiquaries. During this period, he undertook the ordering and labelling of the collections under his care, added to them by judicious and extensive purchases, and helped to build up the collection of JA (Jack) Billmeir, the shipping magnate, which was to come to the museum. It was thanks to Billmeir that the main staircase to the piano nobile of the old Ashmolean was rebuilt.

Josten lived simply in rooms in St John Street surrounded, as later in retirement in Neuss, by carefully chosen objects of beauty and rarity: an armillary sphere, a portrait of Sir Kenelm Digby, and clocks to which he was addicted. He had a wide international acquaintance, and was a notable friend, a punctilious correspondent, amusing and wise.

In the late 1950s he brought to Oxford Helmuth von Moltke and the late Alfred von Stauffenberg, Sippenhaftling of those brought down after the July plot against Hitler in 1944. Their presence opened the eyes of their British contemporaries to the problems of divided loyalties, the insuperable burdens which their families had had to bear under tyranny, and renewed, in a way which has been happily continued, links between an earlier Germany and Oxford.

Following his premature retirement in 1964, at the age of 52, the title of Curator Emeritus was conferred on Josten. He retained a close interest in his museum and the affairs of Oxford, frequently returning until ill-health prevented his doing so. To the end he retained his love for things English. His increasingly battered brown hats had come from Lock, his shoes from Lobb (he did not like criticism of rubber soles), his tweed jackets from Poole. His taste for bonsai trees reflected his interest in the Orient. Although he came from a wealthy family, and retained some of the best pieces of furniture from Glockhammer 42 in Neuss, he lived frugally, being a vegetarian.

By nature a clever, peaceable, spiritual, Catholic man, Kurt Josten was prepared to fight, skilfully and unwearyingly, for what he believed to be right and, above all, for what he believed to be the truth. He had a great gift for friendship and, until he was past 80, kept up those links from his eyrie by letter. He also remained a close friend of England, its achievements and values, to which, as a scholar and gentleman, he made his own unique and loyal contribution.

In the old Ashmolean, his achievements will be recalled for the great contribution which he made to the collections and as Ashmole's remembrancer. In Oxford, he belonged to the generation of Sir Maurice Bowra and Sir Karl Parker, Warden Sparrow and Professor Wind, being, like them, a thorough scholar and a learned and stimulating companion.